Leer for annealing sheet glass



Feb, 3, 192s.

I 1,525,132 H. K. HITCHCOCK LEER FOR ANNEALING SHE-ET GLASS Filed Aug. 18, 1921 3 Sheets-Sheet 1 //v yew 70/? FIE.Z.

LEER FOR ANNEALING SHEET GLASS Filed Aug. 18, 1921 3 Sheets-Sheet 2 Feb. 3, 1925.

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Patented Feb. 3, 1925.

UNITED STATES PATENT OFFICE.

EALBERT K. HITCHCOCK, OF PITTSBURGH, PENNSYLVANIA; ASSIGNOR OF ONE- HALE TO HITCHGOCK EXPERIMENT COMPANY, A CORPORATION OF NEW JERSEY.

LEER FOR ANNE ALING SHEET GLASS.

Application filed August 18, 1921. Serial. No. 493,212.

To all whom it may concern:

Be it known that I, HALBERT K. HITCH- cocK, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have made a new and useful invention in Improvements in Leers for Annealing Sheet Glass, of which the following is a specification.

The invention relates to leers for annealing sheet glass, and more particularly to, an electric leer for annealingvertically drawn sheet glass. It has for its principal objects the provision of an improved construction (1) wherein the relation of the leer to the sheet drawnmay be adjusted bodily to suit requirements, (2) wherein provision is made insuring a uniform temperature on opposite sides of the sheet, and at the opposite edges thereof, (3) wherein provision is made for the expansion and contraction of the electrical heating wires or bands and such elements protected against reaction with the material in which they are mounted, (4) wherein the heating capacity for any particular zone of the leer may be increased or decreased without affecting the uniformity of heat distribution in such zone, and: (5) wherein a high degreeof sensitiveness is secured in the heating element so that the heating effect may be decreased or increased as rapidly as is desirable or necessary. One embodiment of the invention is illustrated in the accompanying drawings, wherein:

Figure 1 is a vertical section through the apparatus; Fig. 2 is a similar section taken at right angles to that of Fig. 1; Fig. 3 is an enlarged "section through one of the blocks carrying a heating element; Figs. 4, 5 and 6 are diagrammatic views showing the arrangement of the heating elements employed, and Fig. 7 is a front elevation on a reduced scale of the block shown in Fig. 3. The glass sheet 1 which is to be annealed is drawn from the bath 2 contained in'the slotted member 3, the character of the bath and apparatus beneath the leer being immaterial, however, in so far as the present invention is concerned. After passing through the leer which comprises the chambers 4, 5, 6 and 7, separated from each other by the diaphragms 8, 9 and 10, the lass enters the drawing device immediately a ove the leer, the lower part of which, only is shown. This drawing device comprises a .ends and about similar pair of endless belts l1 and 11 passing round the pulleys 12 and 13 at their lower pulleys at their upper ends. These endless bands consist of suitable chains passing over sprockets and be- 1ng faced with asbestos members 14 for engaging the surface of the glass. This device serves not only as a means for drawing the glass through the leer below but also serves, to a certain extent, as the leer itself. While the glass is designed to pass through its critical temperature in the leer beneath, it is still at a relatively high temperature when it passes between the endless belts, and these belts with their asbestos covering serve to maintain the heat of the glass and prevent it from cooling too rapidly. The extent to which the glasscools in passing through this drawing device is determined by the length of the device and by the thickness of the asbestos employed or by the use of supplemental devices which might be employed to more or less hasten or retard the cooling of the glass after it passes between the belts.

The leer is preferably :made'in two parts, A and B, althou h this is not necesarily the case, the part while the part A is vertically adjustable, its upper end telescoping inside the part B. This vertical adjustment is secured by hanging the lower 'part A in the channels 15 and supporting such channels upon chains 16 passing around the pulleys 17 and provided with suit-able counterweights so that the leer section will remain in any position to which it is adjusted. The diaphragms' 8, 9 and 10 are each made in two parts with the inner parts opening downwardly around the hinges 18-, the inner parts being supported in the horizontalv position shown when the leer is in operation, by means of the chains 19 secured at their upper ends to the pipe sections 20. In initiating the draw a bait is employed, carried by suitable lifting mechanism extending down from between the drawing belts and through the leer, and at this time the lower section of the leer is moved to its upper position. After the upper. ends of the chains supporting the diaphragm sections are fixed, this movement permits the inner sections of the diaphragms to swing downwardly, thus providing space for the pamage of the bait. After the bait has passed through the leer the four chambers 4.- 5, 6 and 7. In addition to the movement of the lower part A of the leer as above described, it may be advantageous at times to varythe vertical position of the part A during the normal drawing operation, as this will increase or decrease the temperature .at which the sheet enters the leer, the glass which enters the leer, of course, being hotter when the leer is adjusted to a position close to the bath. In such cases the chains 19 are, of, course, adjusted correspondingly so that during the drawing operation the diaphragms are 'in the horizontalpositions illustrated.

The temperature in the chambers 4, 5 and 6 is partially regulated by means of electrically heated elements such as nichrome coils, which are suitably supported in the hollow tile members 21. .The edges of the sheet are heated from the combustion chambers 22 (Fig. 1), heat passing up through the passages 23 adjacent the edges of the sheet. Further supplemental heatingi means are provided in the form of the gas burners 24 opening upwardly at the bottom of the lever and connected to the supply pipe 25.,

The electrical heating wires or bands are preferably mountedas indicated inFig. 3.

The face of theblock 21 is provided with the groove26-which passes back and forth across the face. of the block to give a continuouspassa'ge in whichthewire 27 v may he wound. I This wire is preferably covered with a cotton coating 28 which is soaked with parafiine. The outer opening of the groove is filled with refractory cement, 29. When a heating current is a plied through the Wire 27, the cottoncovering 28 and the parafiinc contained therein are carbonized.

This arrangement servesto give the necessary lost motion in the grooves required by the expansion and contraction of the wire 27, an furthermore serves to insulate the I wires from the clay of the block 21, which is desirable as there is a certain .am ount of chemical reaction between the metal of the wire and the clay when the wire is heated to a high temperature.

The upper section of the leer is entirely heated by electricity; coils being provided at the ends of the leer as well as at the sides thereof. The heating construction at each edge and each side preferably comprises three overlapping coils X Y'Z, as indicated diagrammaticall in Fig. 5. Each circuit is independent an controlled by a suitable switch so that one or more ofthe-sets X Y Z may be cutout of operation. This arrangement serves togive a desirable feature of control. The cutting ou'tof one set of coils does not alter the uniformity of heat throughout the zone since each set is co-extensive vertically with the zone to be heated.

This would not be the case if three se arate coils, one above the other, were employed, in which case the cutting out of one coil would decrease the temperature opposite such coil while the temperature opposite the other coils would remain substantially the same. It is also advantageous to have the plurality of coils instead of a single coil of a corresponding heating capacity, since the radiating surface provided by the plurality of sets is greater than of a single coil of larger cross section and having the same ultimate heating capacity. The element composed of the series of coils will therefore be more sensitive in its operation, and in case of an automatic control such as is effected by thermostatic devices, the element composed of the plurality of heating devices will respond more rapidly than an element composed of a single coil having a larger cross section of wire.

This same construction is applied to all four of the elements as used in connection with the chamber 7. The mounting of the wires in this chamber is preferably accomplished by means of the rods 30 on which the insulators (not shown) are threaded, this method of mounting being preferred here because of the plurality of sets of wires which would make it relatively difiicult to imbed the wires in the faces of the clay blocks, as is the case in the lower part of the leer.

. As indicated in Fig. 4, which illustrates diagrammatically the connections of a single coil of each one of the sets of heating elements, the elements 32 and 33 at the edges 3 of the sheet 1 are mounted on series and this is also the case with the coils XX at the sides of the sheet. It is advantageousto have the coils arranged in series in'this manner as uniform heating of the opposite sides and the opposite edges of the sheet is insured. The coilsopposite the edges of the sheet are preferably placed closer thereto than the coils opposite the sides'of the sheet, as indicatedyin' Fig. 4,;as more heat is required at the edges of the sheet than at the the lower zones of the leer to apply more heat to the edges than to the middle portion. After the sheet becomes uniformly heated this condition does not exist, so that the degree of heat applied to the edges and middle portion of the sheet is uniform. A method of doing this electrically is indicated diagrammatically in Fig. 6, the series of heating coils 32, 32". 32 and 32 opposite the edges of the sheet l, being substituted for the fines 23 of Fig. 1. The heating effect of the coils may be regulated by the rheostats 37, 38 and 39. \Vhen the sheet reaches the uppermost coil it has arrived at a uniform temperature from edge to edge and the degree of heat supplied to the edges and middle at such time is uniform, and decreased the desired amount below that apstantially the same zone in the casing, and

means for supplying current through said sets independently of each other, so that the heating effect may be varied by discontinuing the circuit through one or more of the sets.

2. In a leer for annealing oontinuousl formed sh-eet glass, a casing. means foracl vancing the glass sheet through thecasing, and" electrical heating means comprising a pair of electrically heated elements located .on opposite sides of the sheet, and another pair of such elements located adjacent the opposite edges of the sheet. the elements at the side of the sheet being further removed from the glass than those atthe edges of the sheet.

3.111 a leer for annealing continuously formed sheet glass, a casing, means for advancing the glass sheet through the casing, and electrical heating means comprising a pair of electrically heated-elements located on opposite sides of the sheet, and another pair of such elements located adjacent the opposite edges of the sheet, the elements at the sides of the sheet being in series in one electric circuit and .those' at the edges of the sheet being in another circuit.

4. In combination in a leer for annealing glass drawn vertically from a glass bath, an annealing chamber above the glass, electrical heating means for the chamber and drawing means above the chamber for pulling a glass sheet from the bath and through the chamber.

In combination in a leer for annealing glass drawn vertically from a glass bath, an annealing chamber above the glass, electrical heating means for the chamber, and insulating means above the leer for engaging both sides of the glass sheet throughout its Width and moving therewith for retarding the flow of heat from the sheet.

6. In combination in a leer for annealing glass drawn vertically from a glass bath, an annealing chamber above the glass, electrical heating means for the chamber, drawing means for the glass above the chamber, and means for adjusting the leer vertically.

7. In a glass drawing apparatus an annealing chamber containing a series of electrical heating units arranged in zones one above the other, a means for regulating the energy consumption in the various zones and sect'ionsot' the electrical heaters and a means for passing the drawn sheet through the electrically heated zones.

8. In aleer for-annealing continuously formed sheet glass, a casing, means for advancing the glass sheet through the casing. heating units located on opposite sides of the sheet, andother separate heating units located along the opposite edges of the sheet so that the cooling of the edges of the sheet can be controlled independently of the cooling of the faces of the sheet.

In testimony wvhereot, I have hereunto subscribed my name this 6th day of Aug, 1921.

HALBERT K. HITOHCOCK. 

